Combustion apparatus



Sept. 19, 1967 J. S. WHITESIDES COMBUSTION APPARATUS 2 Sheets-Sheet 1Filed Oct 18, 1965 FIG.

GAS TURBINE INVENTOR J. 5. WHITE SIDES ATTORNEYS FIG. 2

P 1967 r J. 5. WHITESIDES 3,342,241

COMBUSTION APPARATUS Fild Oct. 18, 1965 2 Sheets-Sheet 2 l3 FUEL 8. AIR

INVENTOR J. S.WHITES1DES FIG. 3

ATTORNEYS United States Patent 3,342,241 COMBUSTION APPARATUS John S.Whitesides, Borger, Tex., assignor to Phillips Petroleum Company, acorporation of Delaware Filed Oct. 18, 1965, Ser. No. 496,993 6 Claims.(Cl. 158-7) This invention relates to the recovery of heat. In oneaspect, this invention relates to a method of and apparatus forrecovering the heat in exhaust gases. In another aspect, this inventionrelates to methods of and apparatus for burning a fuel gas to recoverheat therefrom. In a further aspect, this invention relates to burnertips for distributing a fuel gas or the like.

Many power plant installations utilize a gas turbine for generating thepower required. The natural products of combustion in the form ofexhaust gases including free oxygen pass from the gas turbine at atemperature of 700 F. or higher. Except for the use of a small amount ofthis heat for preheating boiler feed water and the like, the heat in theexhaust gases is usually not recovered. Although attempts have been madeto utilize the oxygen in the exhaust gases to support combustion of fuelused to supply heat to a boiler, direct attempts to directly utilize theoxygen in the exhaust gases for supporting combustion to raise thetemperature of the exhaust gases themselves have not been successful inthe art. The reason it is difficult to raise the temperature of theexhaust gases is because it is almost impossible to initiate combustionin the exhaust gas stream as it leaves the gas turbine because of itshigh velocity.

According to this invention, these and other disadvantages of the priorart methods and apparatus for recovering heat from high temperatureexhaust gases are overcome by providing a novel apparatus for effectinga combustion zone in the exhaust gases and for recovering the heatproduced thereby. Another feature of this invention includes a novelburner tip which can be used to supply fuel gas to the stream of exhaustgases in a manner whereby the fuel gas remains ignited even though theexhaust gas is moving at a very high velocity.

The novel apparatus of this invention comprises a duct means adapted toreceive and transmit exhaust gases, a first bank of burners carried bythe wall of said duct means .and arranged in a substantially commonplane which is substantially transverse with the duct means, a secondbank of burners spaced downstream from the first bank of burners andcarried by the walls of the duct means in a substantially common planesubstantially transverse with the duct means, fuel supply meansconnected to each of the first and second banks of burners for supplyingfuel thereto, and heat exchange means connected to the duct meansdownstream from the second bank of burners for recovering the heat inthe exhaust gases passing through the duct means. The duct means of thisinvention can be connected to a gas turbine to receive the exhaust gasestherefrom or to a gas expander. The novel burner tip which can be usedin connection with the heat recovery system of this invention comprisesa tubular body portion having .an inlet end for receiving fuel and anoutlet end for discharging fuel, a shoulder disposed within the tubularbody portion, and means defining a plurality of passageways each ofwhich extends from the shoulder toward the outlet end of the tubularbody. Each 3,342,241 Patented Sept. 19, 1967 of the passageways servesto allow fuel to be projected from within the tubular body in the samegeneral direction as the fuel discharged from the outlet end of thetubular body.

Accordingly, it is an object of this .invention to provide a method ofand apparatus for recovering heat from exhaust gases.

Another object of this invention is to provide a method of and apparatusfor recovering heat from the exhaust gases from a gas turbine.

Still another object of this invention is to provide a method of andapparatus for projecting a flame a maximum distance with a minimumdegree of bending into the stream of exhaust gases from a gas turbine.

A further object of this invention is to provide a burner tip which willretain a flame in high velocity gas streams.

Still another object of this invention is to provide a burner tip whichwill produce an easiiy ignitable gas fuel.

A still further object of this invention is to provide a method andapparatus which eliminates temperature differentials across the exhaustgas stream of a gas turbine.

Another object of this invention is to raise the temperature of theexhaust gases from a gas turbine, and to recover the heat therefrom.

These and other objects of the invention will become apparent to oneskilled in the art after studying the following detailed description,the appended claims, and the accompanying drawings in which:

FIGURE 1 is a diagrammatic illustration of a gas turbine and an exhaustduct for transmitting the products of combustion from the gas turbine;

FIGURE 2 is a cross-section of the exhaust gas duct taken along the line22 of FIGURE 11;

FIGURE 3 is a detail view partially in section showing a burner mountedthrough the wall of the exhaust duct in accordance with the invention;and

FIGURE 4 is a partial cross-section of a burner tip constructed inaccordance with this invention.

Referring now to the drawings wherein like reference numerals are usedto denote like elements, and particularly to FIGURES 1 and 2, theinvention will be described in more detail. A gas turbine 10 is mountedto receive hot gases from a combustor (not shown). The hot gases areexpanded within the turbine and discharged by means of conduit 11 into aduct means 12 which will serve to transmit them to atmosphere. The duct12 is provided with linings 13 and 14 of refractory material which serveto protect the outer shell of the duct 12 from the heat and to preventheat loss.

The normal products of combustion discharged from a gas turbine containabout 18% oxygen. In accordance with this invention, it has beendiscovered that the temperature of the exhaust gases can be raised byutilizing the oxygen in the products of combustion to burn a fuel gas inthe stream of exhaust gases. This can be accomplished by positioning afirst bank of burners, shown generally by reference numeral 16, throughthe walls of the duct 12. A second bank of burners, shown generally byreference numeral 17, is spaced downstream from the first bank ofburners through the walls of the duct 12. The burners in each of thebanks 16 and 17 are arranged in a substantially common plane which issubstantially transverse with the longitudinal axis of the duct 12. Thefirst bank of burners '16 comprises a plurality of individual burners 18positioned radially through and circumferentially spaced around the duct12. The second bank of burners 17 comprises a plurality of individualburners 19 positioned radially through and circumferentially spacedaround duct 12 downstream from the first bank of burners.

Referring more particularly to FIGURE 2, it can be seen that theindividual burners 19 in the second bank of burners 17 are offset withrespect to the individual burners 18 in the first bank of burners 16 inthe sense that none of the burners lie in the same longitudinal plane.Thus, with each bank of burners 16 and 17 comprising ten individualburners, as illustrated, when the burners are circumferentially spacedan equal distance apart, there is a space of about 36 between adjacentburners. By offsetting the second bank of burners 17 with respect to thefirst bank of burners 16 as shown, the net distance between theindividual burners in bothbanks of burners is reduced to about 18. Thisconstruction results in a more uniform distribution of the flame intothe exhaust gases thereby decreasing the temperature differential acrossthe exhaust gases as they pass through duct 12.

A heat exchanger 21 in the form of a helical tube having an inlet tube22 and an outlet tube 23 is connected to and mounted within the duct 12downstream from the second bank of burners 17. This will allow a fluidto be heated by the hot exhaust gases as it is circulated through thehelical tube of the heat exchanger 21.

Referring now to FIGURE 3 of the drawings, a burner of the type 18 and19 in FIGURE 1 of the drawings is illustrated in detail. A cylinder 24constructed of a refractory material or the like is carried by the innersurface of the duct 12 such that the flared portion of the cylinder isoriented toward the center of the duct. A plurality of radialpassageways 26 is provided through the walls of the cylinder 24. Aconduit 27 mounted exteriorly of the duct 12 is positioned in fluidcommunication with cylinder 24. Means including a pipe 28 having a valve29 is operatively connected in fluid communication with conduit 27 forsupplying a combustible mixture of fuel and air for the purpose ofinitiating combustion of the main fuel. An igniter 31 positioned toextend through the surface of pipe 28 will serve to supply a spark toinitiate combustion of the fuel and air mixture.

Each of the burners 18 and 19 is provided with means for receiving fuelin order to sustain combustion after the fuel and air mixture enteringthrough pipe 28 is ignited. This means'includes a fuel delivery pipe 32with a valve 40 therein and a burner tip 33 attached thereto. A tubularhousing 45 mounted within conduit 27 by means of a plurality of spokes35 serves to house the fuel delivery pipe 32 and the burner tip 33 suchthat the burner tip is positioned substantially along the longitudinalaxis of cylinder 24.

The burner tip 33 of this invention is illustrated in more detail inFIGURE 4 of the drawings and comprises 'a tubular body portion having acylindrical inlet end 34 and a frusto-conical outlet end 36. Thecylindrical inlet end 34 can be provided with threads or the like suchthat it can be attached to the fuel supply conduit. If desired, the tip33 can be attached to the fuel supply conduit 32 by welding. Thefrusto-conical outlet end 36 for discharging fuel from the burner tip 33has an interior surface substantially parallel with the frusto-conicalexterior surface. A shoulder 37 is disposed within the tubular body atsubstantially the juncture between the cylindrical inlet end 34 and thefrusto-conical outlet end 36. A pair of parallel passageways 38 disposedwithin the frusto-conical outlet end 36 of the tubular body extend fromthe shoulder 37 through the frusto-conical outlet end in a directionsubstantially parallel with the longitudinal axis of the burner tip 33.

The shoulder 37 of the burner tip 33 can be at any convenient angle withthe interior surface of the burner tip i so long as a smooth transitionof the flowing ga between the cylindrical inlet end and thefrusto-conical outlet end of the burner tip is maintained. Thus, theshoulder can be at an angle of between about 15 and about 75 with aplane transverse to the cylindrical inlet end of the burner tip. Thisrange corresponds to an included angle range between the shoulder 37 andthe interior surface of the cylindrical inlet end of between about andabout The interior surface of the frusto-conical outlet end 36 of theburner tip 33 can be at any convenient angle which will provide thedecrease in the size opening necessary to increase the velocity of thefuel gas. For convenience, it is preferred that the interior surface ofthe frusto-conical outlet end be at an angle of about 80 with a planetransverse to the cylindrical inlet end of the burner tip. This anglecorresponds to an included angle between the interior surface of thefrusto-conical outlet end and the interior surface of the cylindricalinlet end of In the operation of the invention, exhaust gases from gasturbine 10 containing approximately 18% oxygen and at a temperature ofabout 750 F. are introduced into duct means 12 and passed therethroughat hurricane velocity of about 110 feet per second. A fluid such asbutane or the like which is to be heated can be circulated throughhelical heat exchange tube 21 by any suitable pumping means (not shown).The individual burners 18 and '19 can be ignited by introducing amixture of fuel and air through pipe 28. Igniter 31 can be used toignite the combustible mixture whereupon flame will be emitted fromcylinder 24. The main fuel mixture can then be introduced through fueldelivery pipe 32 and burner tip 33 whereupon it will become ignited.After the fuel being delivered from fuel delivery pipe 32 is ignited,the fuel and air mixture supp-lied through pipe 28 can be discontinued.The oxygen carried in'the exhaust gases from the gas turbine will serveto support combustion of the fuel. By igniting all of the burners 18 and19, the temperature of the exhaust gases can be raised by 400 Fahrenheitdegrees or more.

The burner tips of the invention and their association with thecylinders 24 and duct 12 result in a flame having maximum projectioninto the duct with a minimum amount of flame bending in the directionthe exhaust gases travel. This result can be largely attributed to theeffect obtained by the shoulder 37 and its association with thepassageways 38. When the fuel passes through'the burner tip 33, thelayer of fuel adjacent the interior surface of the cylindrical inlet end34 passes smoothly over the shoulder and along the surfaces of thefrusto-conical outlet end. A portion of this layer of fuel-passesthrough passageways 38 such that when this portion leaves passageways 38it serves to maintain the main flame emanating from the outlet end in astraight line. By not allowing the outermost layer of fuel to becomebroken up before it exits from the burner tip, which is made possible bythe presence of the shoulder 37, a much smoother flow of fuel throughthe burner tip is achieved, and a much longer and more durable flameprojection is achieved. Moreover, the fuel passing from passageways 38serves as a constant source of ignition for the fuel exiting through thefrusto-conical outlet end of the burner tip. This advantage allows thefuel to be more easily ignited even when the exhaust gases are travelingat hurricane velocity. Thus, in the event the fuel pressure is reducedsuch that the flame is extinguished, it is easier to ignite the fuelissuing from the flame retention passageways 38.

Another important advantage realized by the method and apparatus of thisinvention is the elimination of hot and cold spots within the exhaustgases in the duct means. This result can be attributed to the presenceof the burners 18 and 19 in their offset relationship.

The following example will serve to illustrate the utility andoperability of the invention. It must be understood that this example isfor the purpose of illustrating typical operating conditions and mustnot be considered to be limiting of the invention.

Example In the apparatus illustrated in FIGURES 1 and 2 using theburners of FIGURES 3 and 4, stable combustion was attained at thefollowing rates and conditions:

Total fuel 1 added to all burners (32):

Heated total admixture (before Temperature, F.

1 Primarily methane.

Although the invention has been described in considerable detail, itmust be understood that such detail is for illustration purposes onlyand must not be considered limiting of the invention.

I claim:

1. Apparatus for recovering waste heat from exhaust gases comprisingduct means adapted to be connected to a gas turbine for receiving andtransmiting exhaust gases therefrom; a first bank of burners carried bythe walls of said duct means and arranged in a substantially commonplane substantially transverse therewith; a second bank of burnerspositioned downstream from said first bank of burners and carried by thewalls of said duct means and arranged in a substantially common planesubstantially transverse therewith, each of the burners in said firstand said second banks of burners comprising a cylinder carried by theinner surface of said duct means, a conduit carried exteriorly of saidduct means in fluid communication with said cylinder, means connected tosaid conduit for supplying a combustible mixture of fuel and airthereto, and means within said conduit for projecting fuel into saidcylinder and said duct means; means connectedto said first and saidsecond banks of burners for supplying fuel thereto; and heat exchangemeans connected to said duct means downstream from said second bank ofburners for recovering the heat in the exhaust gases passing throughsaid duct means.

2. Apparatus according to claim 1 wherein said cylinder of said burneris provided with a plurality of radial passageways extending through thewalls thereof.

3. Apparatus according to claim 1 wherein said means within said conduitfor projecting the fuel into said cylinder and said duct means includesa tubular housing mounted longitudinally within said conduit; a fueldelivery pipe positioned within said housing; and a burner tip attachedto said fuel delivery pipe.

4. Apparatus according to claim 3 wherein said burner tip comprises atubular body portion having an inlet end for receiving fuel and anoutlet end for discharging fuel; a shoulder disposed within said tubularbody; and means defining a plurality of passageways each of whichextends from said shoulder toward the outlet end of said tubular bodyfor allowing fuel to be projected from said tubular body in the samegeneral direction as the fuel discharged from the outlet end of saidtubular body.

5. Apparatus for recovering waste heat from exhaust gases comprisingduct means adapted to receive and transmit exhaust gases; a first bankof burners carried by the walls of said duct means and arranged in asubstantially common plane substantially transverse therewith; a secondbank of burners positioned downstream from said first bank of burnersand carried by the walls of said duct means and arranged in asubstantially common plane substantially transverse therewith, each ofthe burners in said first and second banks of burners comprising acylinder carried by said duct means, a conduit positioned exteriorly ofsaid duct means in fluid communication with said cylinder, meansconnected to said conduit .for supplying a combustible mixture of fueland air thereto, and means within said conduit for projecting fuel intosaid cylinder and said duct means; means connected to said first andsaid second banks of burners for supplying fuel thereto; and heatexchange means connected to said duct means downstream from said secondbank of burners for recovering the heat in the exhaust gases passingthrough said duct means.

6. Apparatus for recovering waste heat from exhaust gases comprisingduct means to receive and transmit exhaust gases; a first bank ofburners carried by the Walls of said duct means and arranged in asubstantially common plane substantially transverse therewith; a secondbank of burners positioned downstream from said first bank of burnersand carried by the wall of said duct means and arranged in asubstantially common plane substantially transverse therewith, theindividual burners of said second bank of burners being offset withrespect to the individual burners of said first bank of burners suchthat the individual burners of said second bank of burners lie inlongitudinal planes different from the longitudinal planes occupied bythe individual burners of said first bank burners; means connected tosaid first and said second banks of burners for supplying fuel thereto;and heat exchange means connected to said duct means downstream fromsaid second bank of burners for recovering the heat in the exhaust gasespassing through said duct means and wherein each of the burners in saidfirst and said second banks of burners comprises a cylinder carried bythe inner surface of said duct means; a conduit carried exteriorly ofsaid duct means in fluid communication with said cylinder; meansconnected to said conduit for supplying a combustible mixture of fueland air to initiate ignition of the fuel; and means within said conduitfor projecting the fuel into said cylinder and said duct means.

References Cited UNITED STATES PATENTS 1,380,507 6/1921 Wallace 239-566X 1,508,718 9/ 1924 Peabody l58-1.5 1,790,908 2/ 1931 Fitts 2395521,824,820 9/1931 Hynes 23712.3 2,444,851 7/1948 Rogers 239548 2,840,0496/1958 Durham 122-7 2,898,093 8/1959 Severson 239-548 X FREDERICK L.MATTESON, JR., Primary Examiner. E. G. FAVORS, Assistant Examiner.

1. APPARATUS FOR RECOVERING WASTE HEAT FROM EXHAUST GASES COMPRISINGDUCT MEANS ADAPTED TO BE CONNECTED TO A GAS TURBINE FOR RECEIVING ANDTRANSMITING EXHAUST GASES THEREFROM; A FIRST BLANK OF BURNERS CARRIED BYTHE WALLS OF SAID DUCT MEANS AND ARRANGED IN A SUBSTANTIALLY COMMONPLANE SUBSTANTIALLY TRANSVERSE THEREWITH; A SECOND BANK OF BURNERSPOSITIONED DOWNSTREAM FROM SAID FIRST BANK OF BURNERS AND CARRIED BY THEWALLS OF SAID DUCT MEANS AND ARRANGED IN A SUBSTANTIALLY COMMON PLANESUBSTANTIALLY TRANSVERSE THEREWITH, EACH OF THE BURNERS IN SAID FIRSTAND SAID SECOND BANKS OF BURNERS COMPRISING A CYLINDER CARRIED BY THEINNER SURFACE OF SAID DUCT MEANS, A CONDUIT CARRIED EXTERIORLY OF SAIDDUCT MEANS IN FLUID COMMUNICATION WITH SAID CYLINDER, MEANS CONNECTED TOSAID CONDUIT FOR SUPPLYING A COMBUSTIBLE MIXTURE OF FUEL AND AIRTHERETO, AND MEANS WITHIN SAID CONDUIT FOR PROJECTING FUEL INTO SAIDCYLINDER AND SAID DUCT MEANS; MEANS CONNECTED TO SAID FIRST AND SAIDSECOND BANKS OF BURNERS FOR SUPPLYING FUEL THERETO; AND HEAT EXCHANGEMEANS CONNECTED TO SAID DUCT MEANS DOWNSTREAM FROM SAID SECOND BANK OFBURNERS FOR RECOVERING THE HEAT IN THE EXHAUST GASES PASSING THROUGHSAID DUCT MEANS.